This invention relates to hanger devices for suspending pipe or casing in wells, and more particularly to a well casing hanger of the expanding type which can be positioned at any desired place in an outer casing string, including the ocean floor, to suspend an inner casing string within the outer casing.
Where wells are drilled in off-shore locations it is generally desirable to suspend the several concentric casing strings of the well at a support point located at or near the ocean floor. Each casing string is suspended from a hanger device which fastens the casing string to the next adjacent outer casing string. While in general these hanger devices operate satisfactorily, there are nevertheless associated problems. One such hanger device, disclosed in U.S. Pat. No. 4,139,059, utilizes a resilient expandable and contractible locking assembly which is machined with frusto-conical tapered surfaces and is of a diameter larger than the bore of the adjacent outer casing. When pushed into the outer casing and contacted therein, the locking assembly is continually self-biased to expand outwardly whereby it is adapted to be run through the outer casing to engage a hanger coupling installed as a segment in the outer casing string at the mudline. The machining of frusto-conical surfaces increases the cost and complexity of such a hanger assembly. In addition, the latching fingers of the locking assembly are of considerable length and are consequently subjected to undesirable bending stresses when the device is operational. Another hanger device, disclosed in U.S. Pat. No. 3,893,714, utilizes a resilient self-expanding locking ring assembly and as an alternative one characterized by a plurality of spring-loaded dogs.
The considerable length and complexity of these assemblies are likewise associated with considerable machining costs and bending stresses which reduce tolerances in regard to material defects.
Accordingly, it is an object of the invention to provide a new and improved well casing hanger assembly which is simple and economical to manufacture.
Another object is to provide an improved well casing hanger assembly of the expanding type which is shorter in length than currently existing hanger assemblies and thereby avoids the imposition of bending stresses on its expander components.
A further object is to provide a new and improved casing hanger assembly of the expanding type which comprises an expandable latching assembly of a plurality of latching fingers which are mounted on the hanger body for pivotal movement about their lower ends and are continually spring biased to expand outwardly at their upper ends to releasably latchingly engage a hanger coupling segment in an outer casing string.